1. Field of the Invention
The invention is related to the field of communications, and in particular, to optical wavelength protection in a communication system.
2. Description of the Prior Art
A Point-of-Presence (POP) is the location where a user exchanges their communications with a communication network. The communication network will have several POPs distributed around a geographic area to exchange communications directly with the users or indirectly with the users through other communication systems. The POP may be comprised of a Synchronous Optical Network (SONET) Add/Drop Multiplexer (ADM). Thus, the SONET ADM exchanges communications with the users either directly or indirectly.
The communication system also includes an optical network to process and transfer the user communications between POPs. Thus, the SONET ADM in a first POP receives communications from a first user system and transfers the communications to the optical network. The optical network processes and transfers the user communications to a second SONET ADM in a second POP. The second SONET ADM transfers the user communications to a second user system. Wavelength Division Multiplexing (WDM) systems in the optical network allow the SONET ADMs to transfer the communications from various users over various optical wavelengths.
The SONET ADMs and the optical network may be configured to form SONET rings. If the optical network experiences a fault, such as a fiber cut, then the SONET ADMs re-route the communications around the other side of the ring. Unfortunately, if the SONET ADM in a POP fails, then the SONET ring protection also fails. Thus, the SONET ADMs do not adequately protect user communications from POP-to-POP.